Sprinkler unit



April 8, 1947. FREEMAN 2,418,765

SPRINKLER UNIT Filed Jan. 4, 1945 I N VEN TOR.

Patented Apr. 8, 1947 SPRINKLER UNIT Howard G. Freeman, Worcester,Mass., assignor to Rockwood Sprinkler Company of Massachusetts,Worcester, Mass, a corporation of Massachusetts Application January 4,1945,'Serial No. 571,219

' .6 Claims. 1

The present invention. relates to sprinkler units for fire extinguishingsystems.

The usual sprinkler head for use in a sprinkler system uses yokes orarms extending from the base of the head to hold the sealing cap. Thisform of head is not satisfactory in many cases. For example, for usewith a fog generating nozzle of the type shown in my Patent No.2,302,021, granted November 17, 1942, the arms create a shadow in thefog pattern and also act as collecting surfaces on which the waterparticles coalesce to form large drops which are highly objectionable infightng many types of fires. In any case, the standard typeof head isunsightly and this has proved to be a deterrent to the use of sprinklersystems in places where appearance is important.

The object of the present invention is to provide a sprinkler unit inwhich the cap is tightly sealed. under inactive conditions without theuse of obtruding arms or yokes, but in which the sealing mechanism isentirely released from the device under active conditions so that thespray pattern is completely unobstructed. A secondary object is toprovide a unit of pleasing appearance.

Various types of sprinkler units, without arms or yokes, have beenproposed but, so far as I am aware, none of these has provedsatisfactory, either because the required sealing pressure could not beobtained or because the fusible mechanism would not be thrown clear ofthe unit when the head is called into operation. It will be understoodthat all parts of the mechanism must remove themselves from the vicinityof the head when the unit is required to operate and this requirement isparticularly important in the case of fog generating units whereobstruction of the spray might be attend-ed with dangerous results.

With the above and other objects in view as will hereinafter appear, theinvention comprises a head having a number of mutually supporting linksor struts, each provided with a fusible member, the several struts beingmounted in such a manner that release of any one of them results in therelease of all. The struts are used to support a holding member engagingwith the cap for sealing the head and this member is also constructed tofree itself from the unit when the struts are released. The inventionalso provides a high sealing pressure, while limiting the stresses .onthe fusible members to safe values.

tional elevation of the head on line 2--2 of Fig, 1; V

Fig. 3 is a side view of one of the strutsand Fig. 4 is a detailed viewillustrating the forces applied to the strut.

The sprinkler head shown in the drawings comprises a base 6 having theusual threaded pipe coupling 8 for attachment to the system. s

The base is provided with a shell or canopy [ll having a cylindricalsidewall l2. The top of the sidewall has a number of bosses l4 extendedinwardly for a slight distance. The bosses are uniformly spaced and, inthe illustrated form of the invention, are three in number.

A nozzle or spray member I6 is secured within the base. The member I6 ishere illustrated as a nozzle having orifices of the type described in myabove mentioned patent to produce a fine fog pattern by internallyimpinging streams of water. The nozzle is normally sealed by adome-shaped cap or closure l8 which closes against finished portion ofthe base member surrounding the nozzle l6.

The cap is held in place by a holding member 20 having a number ofoutwardly extending legs 22. The number of legs may be two or more butpreferably the unit is of tripod form, that is, of three legs, forreasons to be hereinafter explained. Sealing pressure is applied to thecap by means of adjustable central screw 24 by which the pressure may beadjusted to the desiredvalua, As shown in Fig. 2 each leg 22 is curveddownwardly to conform to the general dome shape of the cap and at itsend is provided with an upwardly extending portion 26 having a roundedpoint.

The holding member 20 is retained in position by means of a number ofstruts indicated generally at 28. The struts are equal in number to thelegs 22 (three in the illustrated device), whereby each is engaged byone of the portions 26 of the holding member. Each strut comprises anareshaped link received within the shell and conforming to the curvaturethereof. Near one end each link extends outwardly and i provided with anupward projection 36 toenga-ge under the boss M of the shell. From theprojection 30a short portion 32 of the strut extends in one direction tooverlie the end of the next adjacent strut, and a longer portion 34extends in the other direction to underlie the next strut. As indicatedin the side view of Fig. 3, the long portion 34 of each strut isrecessed at the bottom to receive an upper plate 36, secured thereto bysolder 38 to form the fusible part of the assembly. The upper plate 36slightly overhangs the bottom of the strut and is formed at its end witha bearing point to engage the end of the next adjacent strut. The

points 26 of the tripod engage under the struts at points close to thebosses M. The relations between the length of each strut, its bearingpoint 30 and its point of connection to the tripod leg, are importantand will presently be described in detail. In general, however, it willbe noted that because of the sealing force applied to, the. cap I8, thelegs of the tripod are stressed upwardly and these stresses arecommunicated to the individual struts at the points of contacttherewith. The struts are mutually supported, that is to say, each strutis held in place not only by the bearing 39 but by the struts adjacentthereto. Therefore, if any strut is released by melting of its fusibleportion, all parts of the assembly are without support and are thrownclear of the head. This clearing action is made positive bythespringiness of the arms 22 which are normally under considerablebending stress. It will be noted from Fig. 1 that the arrangement ofparts is such that there is no opportunityfor any part to. catch .on anyother part and the release is thus reliably accomplished.

' It will be understoodthatthe term upward, "over and under refer torelation of the parts in Fig. 3, which show the positions duringassembly. The installed head is usually inverted (or sometimes mountedas shown in Fig. 2).

- In order to describe the necessary dimensional relations for stabilityof the unit, attention may be directed to theforces acting on a singleone of the struts Fig. 4. The point at which the tripod leg engages itisdesignated A, thepoint at which the long portion underlies the nextstrut is designated B, the point ofengagement of the short portion232with the adjacent strut at the other end is designatedB, and'thepointofengagement with the boss zl4;is.designated C.

. :Let F=t-he force. at thecenter of the unit. This is the forcenecessary to hold the head, sealed against any expected pressure and maybe of the order of 1,000 pounds.

Let

FA=the force on the strut at the point A Fs=the force on, the strutateach of the points B, B. a=the distance between C and B. b=theperpendicular distance from B tothe line joining C and B. c=component ofdistance between C and A measured along CB, d=offset between A andmeasured perpendicular to CB, e=component of distancebetweenB' and C indirection-of'CB.

ThenFAis equal to Fdivided'by the number of armslZ. In this case of atripod FA=,1/3F. For stability it is necessary that all moments actingon the strut at point C shall be balanced. Considering moments about theaxisCB,

from which it follows that there will be no unbalanced forces or momentstending to separate the parts, if

Thejterm a-Ferepresents the total length" of the strut as measured alongthe line BC. With this relation of dimensions the device has no tendency4 to come apart, even if dropped or roughly handled.

The foregoing relation is theoretical and is based on a true pointcontact between parts. Since the actual contact is over a small surfaceand there is friction at the contact surfaces, the device will be stableeven with some deviation from the exact relation. If the deviation issufficient to overcome the friction forces, the unit cannot beassembled, or if assembled, may come apart upon being jarred.

It is preferable to make the dimension 0 small relative to a+e, that is,the bearing point A is much closer to C than to the remote end of thestrut. In the structure shown in the drawings, 0 is less than one-tenththe total length, and d bears the same relation to 2). Thus the forceF]; is less than one-tenth the force FA. If th central force F is 1000lbs., FA is 333 lbs. and Fe at the end of the strut is only about 30lbs. From reference to Fig. 3 it will be seen that, owing to the sli htoverhang of the point 46 at the end of the strut, the force on thesoldered joint is still smaller, namely, in the neighborhood of 5 lbs.,which such a joint is well able to withstand over a long inactiveperiod. Nevertheless, upon fusing of the solder there is a sufiicientforce to cause the part 36 to spring away from the'main part of thestrut. As heretofore stated, when any strut fuses, it removes thesupport for the other struts, and thus frees'the tripod and sealing cap.

The holding unit 28 may have any number of legs, two or more, radiatingat equal angles from the center. With only two legs, however, thestresses on the legs and struts are correspondingly increased. If fouror more legs are used, the stresses may be further reduced, but closertolerances may be required to insure equal division of stresses to theseveral struts. With three legs, the stresses carried by the individuallegs and struts are reduced to satisfactory values for most conditions,and this form has the advantage that, since the three tripod pointsdetermine a plane, extreme precision in manufacture is not necessary,and the struts will'be loaded With substantial uniformity even thoughthe parts are constructed with reasonable manufacturing tolerances.

It Will be understood that although the unit is shown as embodied indevice having a special type of nozzle, it may be applied to other formsof spray or sprinkler devices. In any case, the height of the sidewalll2 should be small enough to insure it does not interfere with the spraypattern.

Having thus described the invention, I claim:

1. A sprinkler head having a closure, a supporting base, a plurality ofstruts arranged about the closure in successive overlying and mutuallysupporting relationship, supporting means on the base overlying andengaging the individual struts, and a'pressure member engaging theclosure and having legs underlying and engaging the individual struts,said supporting means retaining the struts in assembled relationshipagainst the pressure exerted thereon by the pressure member,

ing portions underlying and engaging the individual struts, the strutsbeing retained by said points of support against the pressure exertedthereon by the pressure member.

3. A sprinkler head having a closure, a supporting base, a plurality ofstruts arranged about the closure, the base having bosses overlying theindividual struts, the several struts being supported by one another andby said bosses whereby release of any strut removes support for all ofthe struts, and a pressure member engaging the closure and having endsunderlying and engaging the struts, each strut having a portion which isseverable at high temperature.

4. A sprinkler head having a closure, a supporting base, a, plurality ofstruts arranged about the closure in successive overlying and mutuallysupporting relationship, means on the base for overlying and engagingthe individual struts, a pressure member engaging the closure and havinglegs underlying and engaging the individual struts near one end thereof,each strut having a fusible portion near the end remote from the pointof engagement of the pressure member.

5. A sprinkler head having a closure, a supporting base, a plurality ofstruts arranged about the closure, each strut having a single point ofsupport by the base and the several struts having successive overlyingend portions in mutually 6 supporting relationship, a fusible portionnear the end of each strut, and a pressure member engaging the closureand underlying and engaging each individual strut near the end remotefrom the fusible portion and at such a position that moments about thepoint of support on the 1 base are in substantial balance, the strutsbeing retained by said points of support against the pressure exerted bythe pressure member.

f 6. A sprinkler head having a closure, a supporting base, threearc-shaped struts arranged -about the closure, each having a fusibleportion near one end, supporting means on the base overlying each strutnear the other end, the ends of struts being in overlying relationship,a tripod member having a central portion engaging the closure and legsunderlying and engaging the struts near said supporting means, and atsuch positions that all moments on any strut about said supporting meansare in substantial balance.

HOWARD G. FREEMAN.

REFERENCES CITED UNITED STATES PATENTS Name Date Rowley June 2, 1931Number

